1. Field of the Invention
The present invention relates to a radiation image detector in which electrical signals converted by a plurality of image sensing sections arranged in an array are transferred through data lines and integrated by a charge amplifier circuit.
2. Description of the Related Art
Recently, flat panel detectors (FPDs) have been put into practical use. FPD includes an X-ray sensitive layer on a TFT active matrix array and is capable of directly converting X-ray information to digital data. It has advantages over conventional imaging plates in that it allows instantaneous image verification and checking for motion images, and is spreading rapidly.
In a conventional radiation image detector, a semiconductor layer which is conductive for electromagnetic waves is formed on an active matrix substrate having collection electrodes disposed in an array, and an upper electrode is formed on the semiconductor layer. The upper electrode is connected to a high voltage power source. The semiconductor film is a selenium-based amorphous a-Se film with a thickness of 100 to 1000 μm, and generates charges inside of the film when exposed to X-rays.
An equivalent circuit diagram of a conventional radiation image detector is illustrated in FIG. 5.
As illustrated in FIG. 5, a TFT switch 3 and a storage capacitor 2 are provided adjacent to each of collection electrodes disposed on the active matrix substrate in an array. A scanning line 4 is connected to the gate electrode of the TFT switch 3, and a data line 5 is connected to the source electrode. The scanning line 4 is connected to a gate driver IC 40, and the data line 5 is connected to a charge amplifier IC 35 which includes therein a charge amplifier circuit.
A plan view of the conventional radiation image detector is shown in FIG. 6.
An active matrix substrate 10 is formed on a glass substrate 70, and gate driver ICs 40 and charge amplifier ICs 35 are connected to the glass substrate 70 through TCPs 45 and TCPs 36 respectively. Each of the TCPs 36 is connected to a data processing substrate 80 which includes an A/D converter circuit 60 and a control IC 80, and each of the TCPs 45 is connected to a gate substrate 46.
Here, the terminal connection area of the TCP is formed of a film material and influenced largely by linear expansion effects, thus it is said that the arrangement pitch of the wires is limited to 70 μm in a common structure. On the other hand, recent trend in the radiation image detectors is toward a finer pixel pitch, and a pitch of less than 70 μm is demanded.
Making the pixel pitch of the radiation image detector less than 70 μm, however, poses a problem that the TCPs are unable to be mounted in the range of the active matrix substrate of the radiation image detector, since the line pitch in the terminal connection area of the TCP is limited to 70 μm. A larger glass substrate may accommodate the TCPs, but the use of such a large radiation image detector is not practical.
In view of the circumstances described above, it is an object of the present invention to provide a radiation image detector with a pixel pitch of around 50 μm without increasing the size of the detector.